To fully utilize a spectrum, current radio communication systems such as a Code Division Multiple Address (CDMA, Code Division Multiple Address), a Wideband Code Division Multiple Address (WCDMA, Wideband Code Division Multiple Address), a Universal Mobile Telecommunication System (UMTS, Universal Mobile Telecommunication System), a Next Generation Network (LTE, Long Term Evolution) and other networks generally adopt variable envelope modulation technologies capable of performing amplitude modulation and phase modulation at the same time.
The variable envelope modulation technologies need to use a linear amplifier to amplify a signal, which is generally implemented by using a technology based on Envelope Tracking (ET, Envelope Tracking) to ensure linearity and improve power amplification efficiency. As shown in FIG. 1a, after a radio frequency signal is input, a driving amplifier 01 performs driving amplification on the radio frequency signal, and then outputs the radio frequency signal to a radio frequency power amplifier 02; meanwhile, an envelope detector 03 extracts an envelope signal of the radio frequency signal, and a fast tracking power supply 04 amplifies the envelope signal, where the amplified envelope signal is used as a drain voltage of the radio frequency power amplifier; and finally the radio frequency power amplifier 02 outputs the amplified radio frequency signal.
With the development of multi-carrier technologies, the requirements on the bandwidth and efficiency of the fast tracking power supply are increasingly high, and it is difficult to meet the requirements by using a common switch power supply as the fast tracking power supply. Therefore, the prior art provides a novel fast tracking power supply. Referring to FIG. 1b, in the solution, a power supply is divided into two parts: a linear power supply 041 and a switch power supply 042. The linear power supply 041 and the switch power supply 042 are connected in parallel at an output end, and supply power for radio frequency power amplification together. The linear power supply 041 outputs high-frequency power, and the switch power supply 042 outputs low-frequency power. The linear power supply 041 is a voltage source and uses a voltage closed loop to track a high-frequency envelope signal. The switch power supply 042 is a low-frequency current source and uses a current closed loop to detect an output current of the linear power supply 041 and adjust an output current of itself (that is, the switch power supply 042) according to the output current of the linear power supply 041, so that the output current of the linear power supply 041 is as low as possible. In the solution, it is ensured that the output has low distortion through the linear power supply 041, and the whole efficiency is improved through the switch power supply 042.
During the research and implementation of the prior art, the inventors find that the whole power amplification efficiency of the fast tracking power supply in the solution is low.